The present invention relates to a fuser belt and a fusing system for fusing toner images in electrostatographic printing machines.
In electrostatographic printing machines commonly used today, a charge retentive surface is typically charged to a uniform potential and thereafter exposed to a light source to thereby selectively discharge the charge retentive surface to form a latent electrostatic image thereon. The image may be either the discharged portions or the charged portions of the charge retentive surface. The light source may be any well known device such as a light lens scanning system or a laser beam. Subsequently, the electrostatic latent image on the charge retentive surface is rendered visible by developing the image with developer powder referred to in the art as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be a photosensitive member itself or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. In order to fuse toner onto a support surface permanently by heat, it is necessary to elevate the temperature of the toner to a point at which the constituents of the toner coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner cools, solidification of the toner causes it to be firmly bonded to the support
Typically, toner particles are fused to the support by heating to a temperature of between about 90xc2x0 C. to about 160xc2x0 C. or higher depending upon the softening range of the particular resin used in the toner. It is generally undesirable, however, to raise the temperature of the support substantially higher than about 200xc2x0 C. because of the tendency of the support to discolor at such elevated temperatures particularly when the support is paper.
Several approaches to thermal fusing of toner images have been described in the prior art. These methods include providing the application of heat and pressure substantially concurrently by various means: a roll pair maintained in pressure contact; a belt member in pressure contact with a roll; and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner particles takes place when the proper combination of heat, pressure and contact time are provided. The balancing of these parameters to bring about the fusing of the toner particles is well known in the art, and they can be adjusted to suit particular machines or process conditions.
One of the problems with conventional fuser systems is supplying heat for fusing at higher speeds. For example, color xerographic machines require at least four color toner piles to be fixed to the paper at a speed of at least about 20 inches per second. With increased speed and toner/ink pile height, more heat is required to maintain a fixing temperature to assure that the toner is permanently attached to the paper. With certain conventional fuser systems at higher speeds, the core temperature needs to be increased to more than 500xc2x0 F. to maintain the proper surface temperatures for the fusing event. Higher fusing temperatures are undesirable because of power contraints, heat management issues and material limitations. It requires excessive power requirements to achieve higher temperatures, more stringent non-flammable material properties for the fuser elements as well as other components located near the fuser, greater efforts to dissipate heat to prevent overheating of the photoreceptor, toner, and other critical machine parts. Thus, there is a need, which the present invention addresses, for a fuser member and fuser system that reduces the temperature needed to achieve satisfactory fusing.
Conventional fusing members and fusing systems are disclosed in Uehara et al., U.S. Pat. No. 5,345,300; Jacobs, U.S. Pat. No. 5,268,559; Visser et al., U.S. Pat. No. 5,674,621; Schlueter, Jr., U.S. Pat. No. 4,763,158; Vince, U.S. Pat. No. 3,584,195; and Moore et al., U.S. Pat. No. 5,103,263.
In addition, the following document may be relevant: a brochure (10 pages) describing various SIL-PAD(copyright) products.
The present invention is accomplished in embodiments by providing a fuser member for use in an electrostatographic printing machine, comprising:
(a) a substrate layer including a base material and a first thermally conductive additive, wherein the substrate layer is other than a solid layer of a metal or metal alloy; and
(b) an outer toner release layer including an elastomeric material and a second thermally conductive additive, wherein the fuser member is an endless belt that has a thickness ranging from about 3 to about 20 mils.